Interpretive Summary: Plant growth in many production enterprises is affected by diseases that require control to minimize damage to plants. Control methods often involve application of chemicals (fungicides) to suppress growth of the disease-causing organisms. Many fungicides may also contaminate our environment so more benign control measures are needed. We tested a mixture of naturally-occurring microorganisms for effectiveness as a biological control of dollar spot, a serious disease of grasses in lawns and golf courses. This microbial mixture called effective microorganisms (EM) suppressed the growth of the dollar spot fungus and limited damage to grasses in a greenhouse setting. The EM can be prepared by adding a small amount of the microbes to organic materials such as manure and/or food wastes to create a compost called bokashi, which can then be added to grasses like a fertilizer. The results are important to scientists, turfgrass producers, and the horticultural industry because this biologica system can reduce input of chemicals into the environment. Also, organic materials typically handled as wastes can be recycled as useful agents in producing and delivering the effective microorganisms (EM).

Technical Abstract:
Management of Sclerotinia homoeocarpa, causal agent of dollar spot and the most prevalent turfgrass pathogen in North America, is accomplished by use of fungicides. To evaluate effective alternative and more environmentally compatible control approaches, research was conducted to determine (i) effects of Effective Microorganisms (EM) on growth and development of S. homoeocarpa in bioassays and (ii) effects of EM on disease development in turfgrass and turf quality. A laboratory bioassay (in vitro) was conducted on S. homoeocarpa isolated from various turfgrasses using EM on potato dextrose agar (PDA). For the greenhouse study, standard golf-course soil was amended with various rates of EM bokashi made with local organic wastes. The fungus, cultured on autoclaved millet seeds, was inoculated into golf course soils in pots 4 wk after seeding with Penncross creeping bentgrass. Developing turfgrass was evaluated for disease infection and turf quality (disease rating). Laboratory results showed that EM amended in PDA significantly inhibited hyphal growth of S. homoeocarpa. In the greenhouse study, the EM bokashi treatments had significantly less disease 6 wks after seeding than the standard golf-course soil. Increased turf quality was observed with higher EM bokashi concentration. Results suggest that EM cultures can potentially inhibit S. homoeocarpa growth in soil. Further investigations into potential beneficial uses may lead to adaptation of biologically based technology such as EM to develop more sustainable environmental systems.